EBRetryStrategyBackoff (Retry mechanism 0.1.0 API)

java.lang.Object
- com.enigmabridge.retry.EBRetryStrategyBackoff

All Implemented Interfaces:

BackOff, EBRetryStrategy
```
public class EBRetryStrategyBackoff
extends Object
implements BackOff, EBRetryStrategy
```
Implementation of BackOff that increases the back off period for each retry attempt using a randomization function that grows exponentially.

nextBackOffMillis() is calculated using the following formula:
```
 randomized_interval =
 retry_interval * (random value in range [1 - randomization_factor, 1 + randomization_factor])
 
```
In other words nextBackOffMillis() will range between the randomization factor percentage below and above the retry interval. For example, using 2 seconds as the base retry interval and 0.5 as the randomization factor, the actual back off period used in the next retry attempt will be between 1 and 3 seconds.

Note: max_interval caps the retry_interval and not the randomized_interval.

If the time elapsed since an EBRetryStrategyBackoff instance is created goes past the max_elapsed_time then the method nextBackOffMillis() starts returning BackOff.STOP. The elapsed time can be reset by calling reset().

Example: The default retry_interval is .5 seconds, default randomization_factor is 0.5, default multiplier is 1.5 and the default max_interval is 1 minute. For 10 tries the sequence will be (values in seconds) and assuming we go over the max_elapsed_time on the 10th try:
```
 request#     retry_interval     randomized_interval

 1             0.5                [0.25,   0.75]
 2             0.75               [0.375,  1.125]
 3             1.125              [0.562,  1.687]
 4             1.687              [0.8435, 2.53]
 5             2.53               [1.265,  3.795]
 6             3.795              [1.897,  5.692]
 7             5.692              [2.846,  8.538]
 8             8.538              [4.269, 12.807]
 9            12.807              [6.403, 19.210]
 10           19.210              BackOff.STOP
 
```
Implementation is not thread-safe.
Since:

1.15

Author:

Ravi Mistry

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class EBRetryStrategyBackoff.Builder
Builder for EBRetryStrategyBackoff.

Nested Classes
Modifier and Type	Class and Description
`static class`	`EBRetryStrategyBackoff.Builder` Builder for `EBRetryStrategyBackoff`.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`DEFAULT_INITIAL_INTERVAL_MILLIS` The default initial interval value in milliseconds (0.5 seconds).
`static int`	`DEFAULT_MAX_ATTEMPTS` The default maximum number of attempts.
`static int`	`DEFAULT_MAX_ELAPSED_TIME_MILLIS` The default maximum elapsed time in milliseconds (15 minutes).
`static int`	`DEFAULT_MAX_INTERVAL_MILLIS` The default maximum back off time in milliseconds (1 minute).
`static double`	`DEFAULT_MULTIPLIER` The default multiplier value (1.5 which is 50% increase per back off).
`static double`	`DEFAULT_RANDOMIZATION_FACTOR` The default randomization factor (0.5 which results in a random period ranging between 50% below and 50% above the retry interval).
`protected static String`	`FIELD_INITIAL_INTERVAL_MILLIS`
`protected static String`	`FIELD_MAX_ATTEMPTS`
`protected static String`	`FIELD_MAX_ELAPSED_TIME_MILLIS`
`protected static String`	`FIELD_MAX_INTERVAL_MILLIS`
`protected static String`	`FIELD_MULTIPLIER`
`protected static String`	`FIELD_RANDOMIZATION_FACTOR`
`static String`	`NAME`

Fields inherited from interface com.enigmabridge.retry.BackOff
STOP, STOP_BACKOFF, ZERO_BACKOFF

Constructor Summary

Constructors
Modifier	Constructor and Description
	`EBRetryStrategyBackoff()` Creates an instance of ExponentialBackOffPolicy using default values.
`protected`	`EBRetryStrategyBackoff(EBRetryStrategyBackoff.Builder builder)`
	`EBRetryStrategyBackoff(org.json.JSONObject json)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`EBRetryStrategy`	`copy()`
`int`	`getCurrentIntervalMillis()` Returns the current retry interval in milliseconds.
`long`	`getElapsedTimeMillis()` Returns the elapsed time in milliseconds since an `EBRetryStrategyBackoff` instance is created and is reset when `reset()` is called.
`int`	`getInitialIntervalMillis()` Returns the initial retry interval in milliseconds.
`int`	`getMaxAttempts()` Return the maximum number of tries that will be attempted for the EBRetryJob instance.
`int`	`getMaxElapsedTimeMillis()` Returns the maximum elapsed time in milliseconds.
`int`	`getMaxIntervalMillis()` Returns the maximum value of the back off period in milliseconds.
`double`	`getMultiplier()` Returns the value to multiply the current interval with for each retry attempt.
`String`	`getName()`
`double`	`getRandomizationFactor()` Returns the randomization factor to use for creating a range around the retry interval.
`long`	`getWaitMilli()`
`long`	`nextBackOffMillis()` Gets the number of milliseconds to wait before retrying the operation or `BackOff.STOP` to indicate that no retries should be made.
`long`	`nextBackOffMillis(boolean inc)`
`void`	`onFail()`
`void`	`onSuccess()`
`void`	`reset()` Sets the interval back to the initial retry interval and restarts the timer.
`boolean`	`shouldContinue()`
`org.json.JSONObject`	`toJSON(org.json.JSONObject json)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - NAME
```
public static final String NAME
```
    See Also:
    
    Constant Field Values
  - DEFAULT_INITIAL_INTERVAL_MILLIS
```
public static final int DEFAULT_INITIAL_INTERVAL_MILLIS
```
    The default initial interval value in milliseconds (0.5 seconds).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_RANDOMIZATION_FACTOR
```
public static final double DEFAULT_RANDOMIZATION_FACTOR
```
    The default randomization factor (0.5 which results in a random period ranging between 50% below and 50% above the retry interval).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MULTIPLIER
```
public static final double DEFAULT_MULTIPLIER
```
    The default multiplier value (1.5 which is 50% increase per back off).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_INTERVAL_MILLIS
```
public static final int DEFAULT_MAX_INTERVAL_MILLIS
```
    The default maximum back off time in milliseconds (1 minute).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_ELAPSED_TIME_MILLIS
```
public static final int DEFAULT_MAX_ELAPSED_TIME_MILLIS
```
    The default maximum elapsed time in milliseconds (15 minutes).
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_ATTEMPTS
```
public static final int DEFAULT_MAX_ATTEMPTS
```
    The default maximum number of attempts.
    
    See Also:
    
    Constant Field Values
  - FIELD_INITIAL_INTERVAL_MILLIS
```
protected static final String FIELD_INITIAL_INTERVAL_MILLIS
```
    See Also:
    
    Constant Field Values
  - FIELD_RANDOMIZATION_FACTOR
```
protected static final String FIELD_RANDOMIZATION_FACTOR
```
    See Also:
    
    Constant Field Values
  - FIELD_MULTIPLIER
```
protected static final String FIELD_MULTIPLIER
```
    See Also:
    
    Constant Field Values
  - FIELD_MAX_INTERVAL_MILLIS
```
protected static final String FIELD_MAX_INTERVAL_MILLIS
```
    See Also:
    
    Constant Field Values
  - FIELD_MAX_ELAPSED_TIME_MILLIS
```
protected static final String FIELD_MAX_ELAPSED_TIME_MILLIS
```
    See Also:
    
    Constant Field Values
  - FIELD_MAX_ATTEMPTS
```
protected static final String FIELD_MAX_ATTEMPTS
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - EBRetryStrategyBackoff
```
public EBRetryStrategyBackoff()
```
    Creates an instance of ExponentialBackOffPolicy using default values.
    
    To override the defaults use EBRetryStrategyBackoff.Builder.
    - initialIntervalMillis defaults to DEFAULT_INITIAL_INTERVAL_MILLIS
    - randomizationFactor defaults to DEFAULT_RANDOMIZATION_FACTOR
    - multiplier defaults to DEFAULT_MULTIPLIER
    - maxIntervalMillis defaults to DEFAULT_MAX_INTERVAL_MILLIS
    - maxElapsedTimeMillis defaults in DEFAULT_MAX_ELAPSED_TIME_MILLIS
    - maxAttempts defaults in DEFAULT_MAX_ATTEMPTS
  - EBRetryStrategyBackoff
```
public EBRetryStrategyBackoff(org.json.JSONObject json)
```
  - EBRetryStrategyBackoff
```
protected EBRetryStrategyBackoff(EBRetryStrategyBackoff.Builder builder)
```
    Parameters:
    
    builder - builder
- Method Detail
  - nextBackOffMillis
```
public long nextBackOffMillis()
                       throws IOException
```
    Gets the number of milliseconds to wait before retrying the operation or BackOff.STOP to indicate that no retries should be made.
    Example usage:
```
     long backOffMillis = backoff.nextBackOffMillis();
     if (backOffMillis == Backoff.STOP) {
     // do not retry operation
     } else {
     // sleep for backOffMillis milliseconds and retry operation
     }
 
```
    This method calculates the next back off interval using the formula: randomized_interval = retry_interval +/- (randomization_factor * retry_interval)
    
    Subclasses may override if a different algorithm is required.
    Specified by:
    
    nextBackOffMillis in interface BackOff
    
    Returns:
    
    long
    
    Throws:
    
    IOException - IO exceptions only (beyond software control)
  - nextBackOffMillis
```
public long nextBackOffMillis(boolean inc)
                       throws IOException
```
    Throws:
    
    IOException
  - getInitialIntervalMillis
```
public final int getInitialIntervalMillis()
```
    Returns the initial retry interval in milliseconds.
    
    Returns:
    
    int
  - getRandomizationFactor
```
public final double getRandomizationFactor()
```
    Returns the randomization factor to use for creating a range around the retry interval.
    
    A randomization factor of 0.5 results in a random period ranging between 50% below and 50% above the retry interval.
    
    Returns:
    
    double
  - getCurrentIntervalMillis
```
public final int getCurrentIntervalMillis()
```
    Returns the current retry interval in milliseconds.
    
    Returns:
    
    int
  - getMultiplier
```
public final double getMultiplier()
```
    Returns the value to multiply the current interval with for each retry attempt.
    
    Returns:
    
    double
  - getMaxIntervalMillis
```
public final int getMaxIntervalMillis()
```
    Returns the maximum value of the back off period in milliseconds. Once the current interval reaches this value it stops increasing.
    
    Returns:
    
    int
  - getMaxAttempts
```
public final int getMaxAttempts()
```
    Return the maximum number of tries that will be attempted for the EBRetryJob instance.
    
    Returns:
    
    int
  - getMaxElapsedTimeMillis
```
public final int getMaxElapsedTimeMillis()
```
    Returns the maximum elapsed time in milliseconds.
    
    If the time elapsed since an EBRetryStrategyBackoff instance is created goes past the max_elapsed_time then the method nextBackOffMillis() starts returning BackOff.STOP. The elapsed time can be reset by calling reset().
    
    Returns:
    
    int
  - getElapsedTimeMillis
```
public final long getElapsedTimeMillis()
```
    Returns the elapsed time in milliseconds since an EBRetryStrategyBackoff instance is created and is reset when reset() is called.
    
    The elapsed time is computed using System.nanoTime().
    
    Returns:
    
    long
  - getName
```
public String getName()
```
    Specified by:
    
    getName in interface EBRetryStrategy
  - onFail
```
public void onFail()
```
    Specified by:
    
    onFail in interface EBRetryStrategy
  - onSuccess
```
public void onSuccess()
```
    Specified by:
    
    onSuccess in interface EBRetryStrategy
  - reset
```
public final void reset()
```
    Sets the interval back to the initial retry interval and restarts the timer.
    
    Specified by:
    
    reset in interface BackOff
    
    Specified by:
    
    reset in interface EBRetryStrategy
  - shouldContinue
```
public boolean shouldContinue()
```
    Specified by:
    
    shouldContinue in interface EBRetryStrategy
  - getWaitMilli
```
public long getWaitMilli()
```
    Specified by:
    
    getWaitMilli in interface EBRetryStrategy
  - copy
```
public EBRetryStrategy copy()
```
    Specified by:
    
    copy in interface EBRetryStrategy
  - toJSON
```
public org.json.JSONObject toJSON(org.json.JSONObject json)
```
    Specified by:
    
    toJSON in interface EBRetryStrategy

Class EBRetryStrategyBackoff

Nested Class Summary

Field Summary

Fields inherited from interface com.enigmabridge.retry.BackOff

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NAME

DEFAULT_INITIAL_INTERVAL_MILLIS

DEFAULT_RANDOMIZATION_FACTOR

DEFAULT_MULTIPLIER

DEFAULT_MAX_INTERVAL_MILLIS

DEFAULT_MAX_ELAPSED_TIME_MILLIS

DEFAULT_MAX_ATTEMPTS

FIELD_INITIAL_INTERVAL_MILLIS

FIELD_RANDOMIZATION_FACTOR

FIELD_MULTIPLIER

FIELD_MAX_INTERVAL_MILLIS

FIELD_MAX_ELAPSED_TIME_MILLIS

FIELD_MAX_ATTEMPTS

Constructor Detail

EBRetryStrategyBackoff

EBRetryStrategyBackoff

EBRetryStrategyBackoff

Method Detail

nextBackOffMillis

nextBackOffMillis

getInitialIntervalMillis

getRandomizationFactor

getCurrentIntervalMillis

getMultiplier

getMaxIntervalMillis

getMaxAttempts

getMaxElapsedTimeMillis

getElapsedTimeMillis

getName

onFail

onSuccess

reset

shouldContinue

getWaitMilli

copy

toJSON